A multitude of wells have been drilled into earth strata for the extraction of oil, gas, and other material there from. In many cases, such wells are found to be initially unproductive, or may decrease in productivity over time, even though it is believed that the surrounding strata still contains extractable oil, gas, water or other material. Such wells are typically vertically extending holes including a casing usually of a mild steel pipe having an inner diameter of from just a few inches to over eight inches used for the transportation of the oil, gas, or other material upwardly to the earth's surface. In other instances, the wellbore may be uncased at the zone of interest, commonly referred to as an “openhole” completion.
In an attempt to obtain production from unproductive wells and increase production in under producing wells, methods and devices for forming a hole in a well casing, if present, and forming a lateral passage there from into the surrounding earth strata are known. For example, a hole in cased wells can be produced by punching a hole in the casing, abrasively cutting a hole in the casing, milling a hole in the casing wall or milling out a vertical section of casing. While more or less efficacious, such methods are generally familiar to those in the art. In openhole wells, the steps to form a hole in the casing are not required, but the methods for forming a lateral passage into the surrounding strata may be virtually identical to those used on cased well.
Under both the cased and uncased well scenarios, a type of whipstock is typically incorporated to direct the cutting head out of the wellbore and into the formation. The whipstock may be set on the end of production tubing. Because of the time and economic benefits, often the cutting tools are run on the end of coiled tubing. In at least one known conventional horizontal drilling method using coiled tubing, the cutting tool completes its transition to the horizontal direction over a radius of at least several feet and some methods require a radius of over 100 feet. The size of the radius stems primarily from the length and diameter of the cutting tools and the rigidity of the toolstring that must transition around the radius. Other known methods for creating horizontal drainage tunnels are able to transition a much tighter radius (e.g., within 4.5″ casing) by not attempting to pass relatively long and/or large diameter tools (e.g., a mud motor) outside of the wellbore. Instead most such methods utilize a flexible jetting hose with a specialized and relatively small nozzle head (e.g., less than a few inches long). Such methods may be efficacious, but typically suffer from a common problem that that they do not and/or cannot provide adequate torque to satisfactorily power a mechanical cutting means capable of cutting harder formation. Accordingly, these methods may be limited only to very soft formations.
In some instances, greater efforts are being expended at producing thinner, laminated reservoirs that may not have been produced in the past. Further, older, abandoned reservoirs are being reworked using enhanced oil recovery (EOR) and other techniques to extract as much remaining oil and gas as possible in contrast to past practices where such an older well may have been simply abandoned. To meet the requirements of today's more complex oil and gas recovery methods, more specifically, short radius horizontal drilling, there is a growing need to obtain real-time visual imaging of the amount of hydrocarbons being produced through perforations in the casing of a cased-hole completion or simply from the formation in an openhole completion. The imaging purpose is to guide, steer, position and orient short radius horizontal drilling tools after capturing the images, and without removing the tool string, to include the visual imaging device, from the borehole, proceed to perform the short radius drilling operation. The apparatus purpose is also to only run in hole the imaging device one time thereby reducing the amount of time on location and reduce the costs associated with running in and pulling out of the hole.
One aspect of utilizing a whipstock with downhole tools to the placement of the whipstock and the tools that will be used to form the lateral borehole extending into the formation. The placement, both the depth and axially is important to direct the cutting head out of the wellbore and into the formation of interest and can be assisted with the use of a visual imaging device. The visual imaging device can be used to locate and position the whipstock at the optimal depth and/or azimuth of the formation of interest so as to guide, steer, position and orient short radius horizontal drilling tools can enable production from thinner reservoirs that heretofore have not been developed.
In view of the above, it would be desirable to have a the ability to locate and position a whipstock at an optimal depth and/or azimuth of the formation of interest to guide, steer, position and orient short radius horizontal drilling tools to produce lateral boreholes into a formation of interest. It would further be desirable to have a cutting system capable of locating a whipstock and other tools such as a cutting tool in a wellbore to precisely position such tools with the aid of a visual imaging device.